Messages in this thread | | | From | David Howells <> | Subject | Re: file metadata via fs API (was: [GIT PULL] Filesystem Information) | Date | Wed, 12 Aug 2020 14:33:13 +0100 |
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Miklos Szeredi <miklos@szeredi.hu> wrote:
> You said yourself, that what's really needed is e.g. consistent > snapshot of a complete mount tree topology. And to get the complete > topology FSINFO_ATTR_MOUNT_TOPOLOGY and FSINFO_ATTR_MOUNT_CHILDREN are > needed for *each* individual mount.
That's not entirely true.
FSINFO_ATTR_MOUNT_ALL can be used instead of FSINFO_ATTR_MOUNT_CHILDREN if you want to scan an entire subtree in one go. It returns the same record type.
The result from ALL/CHILDREN includes sufficient information to build the tree. That only requires the parent ID. All the rest of the information TOPOLOGY exposes is to do with propagation.
Now, granted, I didn't include all of the topology info in the records returned by ALL/CHILDREN because I don't expect it to change very often. But you can check the event counter supplied with each record to see if it might have changed - and then call TOPOLOGY on the ones that changed.
If it simplifies life, I could add the propagation info into ALL/CHILDREN so that you only need to call ALL to scan everything. It requires larger buffers, however.
> Adding a few generic binary interfaces is okay. Adding many > specialized binary interfaces is a PITA.
Text interfaces are also a PITA, especially when you may get multiple pieces of information returned in one buffer and especially when you throw in character escaping. Of course, we can do it - and we do do it all over - but that doesn't make it efficient.
David
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